Question: Nadia starts counting at 21, and she counts by fives. If 21 is the 1st number that Nadia counts. what is the 15th number that she counts?
What is the first number that she counts? $21$ What is the second number that she counts? $\begin{align*}&21 + 5 \\ &= 26\end{align*}$ What is the third number that she counts? $\begin{align*}&21 + 5 + 5 \\ &= 21 + (2 \times 5) \\ &= 31\end{align*}$ What is the 15th number that she counts? $\begin{align*}&21 + (14\times5) \\ &= 21 + 70 \\ &= 91\end{align*}$